This invention relates to an improved releasable coupling assembly for connecting a spray tube to a drive mechanism in an oscillating wave lawn sprinkler. More specifically, the releasable coupling assembly of this invention comprises an improvement over the releasable coupling means disclosed and claimed in U.S. Pat. No. 4,140,278.
A typical oscillating wave lawn sprinkler includes a water-driven motor for oscillating a spray tube through a prescribed rotational movement generally about its own axis. More particularly, water supplied to the sprinkler flows initially into association with the motor, which provides a rotary output translated in turn through a mechanical linkage to drive the spray tube through an angularly oscillatory motion. This linkage connection to the spray tube is adjustable to provide for spray tube travel through different selected arcuate paths. The spray tube is typically formed from light-weight aluminum and the linkage is typically constructed from lightweight molded plastic, which is subject to breaking when other than rotational drive forces are applied to the sprinkler. Such exterior forces can be generated, for example, by kicking or by inadvertent impact of a ball.
In U.S. Pat. No. 4,140,278, a releasable coupling means is disclosed for connecting the spray tube of an oscillating wave lawn sprinkler to the spray tube linkage means, thereby allowing the spray tube to disengage from the linkage means when the lawn sprinkler is subjected to an external rotational force exceeding a predetermined magnitude. This has the intended benefit of preventing damage to the plastic drive mechanism of the lawn sprinkler; however, a variety of disadvantages have limited the commercial utility of lawn sprinklers constructed in accordance with this patent. For example, the force required to cause the coupling means to disengage from the spray tube is relatively high, resulting in situations wherein sufficient force is applied to the sprinkler to damage the drive mechanism but not to disengage the coupling means. Moreover, the releasable coupling means requires multiple additional structural components including interfitting collars and a sleeve, thereby unduly increasing the cost of the sprinkler and making assembly of the sprinkler more complex. Further, the provision of additional structural components increases the risk of component failure during operation of the sprinkler.
The present invention overcomes the problems and disadvantages of the sprinkler in U.S. Pat. No. 4,140,278 by providing an improved releasable coupling assembly having a minimum number of components for connecting the water-driven drive linkage to the oscillatory spray tube, and for permitting release of the spray tube in response to relatively low disengagement forces.